Changes in δ 13 C values during drought Provenance and drought significantly influenced δ 13 C values, soil quality had a marginally significant effect ( p = .077), and interactions were nonsignificant (Fig. 1 , Table 3 ).
However, saplings from Montejo de la Sierra produced more new leaves between early May and mid‐June compared to plants from Kempten and Johanniskreuz, which was significant for sandy soil and a nonsignificant trend for loamy soil.
Saplings on sandy soil showed a trend toward a larger change in δ 13 C suggesting higher stress than in loamy soil.